Spiral drill collar and method of manufacture thereof



L. F. SHIPLET Sept. 14, 1965 SPIRAL DRILL COLLAR AND METHOD OFMANUFACTURE THEREOF Filed Oct. 21, 1965 United States Patent f 3,205,733SPIRAL DRILL COLLAR AND METHOD OF MANUFACTURE THEREOF Levi F. Shiple't,Houston, Tex., assignor to Texaco Inc.,

New York, N.Y., a corporation of Delaware Filed Oct. 21, 1963, Ser. No.317,593 11 Claims. (Cl. 76108) This invention relates generally to therotary drilling of wells and specifically to an improved drill collarand the method of manufacture thereof.

' In rotary drilling, the bit is rotated, with weight being applied tothe bit to obtain effective cutting. As the well bore increases indepth, lengths of drill pipe, each normally 30 feet long, are added toform the drill stern, which includes the drill collar, distinct from thedrill pipe, adjacent the bit. Through this drill stern, drilling fluidsare provided to the bottom of the well bore where the bit cuttings arepicked up by the fluids and brought to the surface through the annulusdefined by the well bore and/ or casing and the drill stem.

Conventional drill collars are made of solid steel billets, usually 30feet long, to obtain the necessary weight, with the center machined out,e.g. by boring, to the desired inside diameter to define an axialpassage. The drill collar is essential to drilling operations becausethrough its weight and rigidity, it helps to keep the drilling of a borehole straight. Its weight on the bit does not apply compression on thedrill pipe and thereby aids in avoiding hole deviation. Frequently,where certain sedimentary formations are abrasive and have low dipangles where fracturing and faulting occur frequently, deviation controlbecomes difficult.

Accordingly, it is an object of the invention to provide an improveddrill collar which will increase the penetration rate of drillingwithout excessive hole deviation.

It is another object of the invention to provide an improved drillcollar which will improve the speed of flow of drilling fluids from thebottom to the top of the well bore and also more easily lift bitcuttings and help to keep the drill bit clean.

Still another object of the invention is to provide an improved drillcollar which will act as a stabilizer and hold more weight on a drillbit.

Another object of the invention is to provide an improved drill collarhaving substantially the same diametral dimension as the drill bit.

Still another object of the invention is to provide a novel method ofmanufacture of a spiral drill collar.

These and other objects, advantages and features of the presentinvention will become apparent from the following description of theinvention and by reference to the accompanying drawings wherein:

FIG. 1 is a longitudinal View, partly in section, of the embodiment ofthe drill collar constructed in accordance with the present invention,with an intermediate portion thereof broken away;

FIG. 2 is a cross sectional view on an enlarged scale of a square billetshowing the distortion of the original flat faces after twisting and theextent the original corners are cut away; and

FIG. 3 is a cross sectional view, on an enlarged scale, taken along line3-3 of FIGURE 1, of the spiral drill collar as positioned in a wellbore.

In accordance with the illustrated embodiment of my invention, there isshown an improved drill collar which fits into a well bore with closeclearance to provide stability and to add more weight on the bit therebyimproving deviation control and return flow of fluids and increasingdrilling speed.

Referring to FIG. 1, the drill collar constructed accord- 3,205,733Patented Sept. 14, 1965 ing to my invention is disclosed at 10, havingan upper end 11 formed into a cylindrical neck with a threaded box 12formed therein. The lower end 13 is also formed into a cylindrical neckfor the threaded pin 14, which receives the bit sub 15 for holding asuitable rotary type bit 16. There is also disclosed the manner in whicha pin 17 at the lower end 18 of another drill collar or a drill pipe isjoined to box 12 to form the drill stem. The axial passage through thedrill collar is disclosed at 19. The cylindrical necks can be formed byswaging or by machining, e.g. by turning, the square billet at the timethat the axial passage is formed, e.g. by boring, and either before orafter the billet is twisted.

FIG. 2 discloses the deformation of the original flat faces of thesubstantially square billet into concave surfaces, resulting when thesquare billet is twisted counterclockwise about its longitudinal axis ofits 30 foot length to provide substantially a right hand screw thread.The amount of twisting is varied according to the type formation beingdrilled, the velocity of the drilling fluids in the annulus and therotating speed of the drill string. The corners of the original squarebillet, indicated as a, b, c and d, should be machined off to give thedesired crosssection dimension and to obtain adequate bearing surfaceagainst the well bore, the machining to include grinding, turning and/or hogging. The rounding of the corners is indicated at A, B, C, D bydotted lines in FIG. 2 and by solid lines in FIG. 3. The original fiatfaces, indicated by dotted lines between the corners, now take theconcave shape surfaces as indicated in full lines in FIG. 2. The size ofthe billet is chosen so that its diagonal dimension is slightly largerthan the well bore diameter or that of the drill bit so that after it istwisted and the corners machined off, the outside diameter will beslightly less than the diameter of the well bore. This will create apackedhole effect and tend to prevent deviation of the hole.

FIG. 3 discloses in cross section the filling or packed position of thespiral drill collar in the bore hole, showing the close contact of thebearing surfaces A, B, C, D at the rounded off corners with the wellbore, the flutelike flights formed from the flat face surfaces of thesquare billet serving as an auger for easy removal of the bit cuttingsfrom the bottom of the well bore along with the drilling fluids. Therotation of the spiral drill collar during drilling provides the liftingeffect to the drilling fluids and bit cuttings, and the bearing surfacesact as a stabilizer because of the screw effect on the walls of the wallbore, thus reducing the need of separate stabilizers on the drill stemabove the bit.

As indicated in FIG. 1, conventional drill collars may be used above theimproved spiral drill collar, and where formally a conventional rounddrill collar would permit weights from 2,000 to 5,000 pounds to beapplied on the bit, beyond which weights, considerable hole deviationwould occur, the spiral drill collar formed by twisting a square billetcan carry 20,000 to 40,000 pounds of weight with 8% inch drill pipewithout excessive hole deviation. Also, two twists per 30 feet of drillcollar is considered usual.

Thus, there has been disclosed and described a novel and improved drillcollar and method of manufacture thereof, which by putting a twist in asquare billet, cuts down on the number of separate stabilizers used,eases the return of drilling fluids and cuttings from the bottom of thebore hole to the surface, and by allowing the application of additionalweight on the drill bit, shortens the drilling time because of theincreased penetration rate and thus reduces the cost of the drilling.

Other modifications and variations of the invention as hereinbefore setforth may be made without departing from the spirit and scope thereof,and therefore only 3 such limitations should be imposed as are indicatedin the appended claims.

I claim: 1. The method of forming a spiral drill collar for use with abit having substantially the same outer diametral dimension comprisingin said twisting comprises two counterclockwise complete turns aboutsaid longitudinal axis.

3Q The'method as defined by step (b) of claim 1, where- 'in the formingof the ends into cylindrical necks is accomplished by swaging. I

4. The method as defined by step ('c) of claim 1, when said screwthreading comprises the external threading of a pin at one end of saidmember and an internal threading of a box at the other end of saidmember.

5. The method as defined by step (d) of claim 1, wherein said roundingof theedges is accomplished by a machining process.

6. In a method of forming a spiral drill collar of normal length from asubstantially square billet, the steps of (a) providing cyindrical necksat the ends of said billet;

(b) forming an axial passage through said billet;

(c) twisting said billet in counterclockwise direction about itslongitudinal axis;

((1) providing each of said cylindrical necks with screw threading; andq (e) machining the original edges of said billet to ob- 4 tain a drillcollar of the desired dimensions an having spiral grooves.

7. method as defined by step (a) of claim 6, wherein said cylindricalnecks are formed by machining.

8. The method as defined 'by step (a) of claim 6, wherein saidcylindrical necks are formed by swaging.

9. The method as defined by step (c) of claim 6, wherein said twistingprovides two complete turns.

10. The method as defined by step (d) of claim 6, wherein opposite necksof said collar are provided respectively with internal and externalthreading.

11. The method of forming aspiraldrill collar for use with a bit havingsubstantially the same outer diametral dimension comprising (a) formingthe ends of a square hollow member into cylindrical necks; (b)twisting'said-s'quare' hollow member with cylindrical ends about itslongitudinal axis; (c) providing said cylindrical necks at each of theends of said twisted member with screw threading;

and

(d) rounding the original edges of said square hollow member to providesaid drill collar with the desired diametral dimension;

GRANVILLE Y. CUSTER, JR., Primary Examiner. CARL W. TQMLIN, Examiner,

1 1/ 26 Great Britain.

1. THE METHOD OF FORMING A SPIRAL DRILL COLLAR FOR USE WITH A BIT HAVINGSUBSTANTIALLY THE SAME OUTER DIAMETRAL DIMENSION COMPRISING (A) TWISTINGA SQUARE HOLLOW MEMBER ABOUT ITS LONGITUDINAL AXIS; (B) FORMING THE ENDSOF THE RESULTING TWISTED MEMBER INTO CYLINDRICAL NECKS; (C) PROVIDINGSAID CYLINDRICAL NECKS AT EACH OF THE ENDS OF SAID TWISTED MEMBER WITHSCREW THREADING; AND (D) ROUNDING THE ORIGINAL EDGES OF SAID SQUAREHOLLOW MEMBER TO PROVIDE SAID DRILL COLLAR WITH THE DESIRED DIAMETRALDIMENSION.